Hypnotherapy involves achieving a psychological state of awareness that is different from the ordinary state of consciousness. While in a hypnotic state, a variety of phenomena can occur. These phenomena include alterations in memory, heightened susceptibility to suggestion, paralysis, sweating, and blushing. All of these changes can be produced or removed in the hypnotic state. Many studies have shown that roughly 90% of the population is capable of being hypnotized.
In 2011, a Russian "evil hypnotist" was suspected of tricking customers in banks around Stavropol into giving away thousands of pounds worth of money. According to the local police, he would approach them and make them withdraw all of the money from their bank accounts, which they would then freely give to the man.[158] A similar incident was reported in London in 2014, where a video seemingly showed a robber hypnotizing a shopkeeper before robbing him. The victim did nothing to stop the robber from looting his pockets and taking his cash, only calling out the thief when he was already getting away.[159][160]

Ernest Hilgard, who developed the "neodissociation" theory of hypnotism, hypothesized that hypnosis causes the subjects to divide their consciousness voluntarily. One part responds to the hypnotist while the other retains awareness of reality. Hilgard made subjects take an ice water bath. None mentioned the water being cold or feeling pain. Hilgard then asked the subjects to lift their index finger if they felt pain and 70% of the subjects lifted their index finger. This showed that, even though the subjects were listening to the suggestive hypnotist, they still sensed the water's temperature.[180]
Hypnosis has long been considered a valuable technique for recreating and then studying puzzling psychological phenomena. A classic example of this approach uses a technique known as posthypnotic amnesia (PHA) to model memory disorders such as functional amnesia, which involves a sudden memory loss typically due to some sort of psychological trauma (rather than to brain damage or disease). Hypnotists produce PHA by suggesting to a hypnotized person that after hypnosis he will forget particular things until he receives a “cancellation,” such as “Now you can remember everything.” PHA typically only happens when it is specifically suggested and it is much more likely to occur in those with high levels of hypnotic ability, or “high hypnotizable” people. Now a new study shows that this hypnotic state actually influences brain activity associated with memory.
Whereas the older "depth scales" tried to infer the level of "hypnotic trance" from supposed observable signs such as spontaneous amnesia, most subsequent scales have measured the degree of observed or self-evaluated responsiveness to specific suggestion tests such as direct suggestions of arm rigidity (catalepsy). The Stanford, Harvard, HIP, and most other susceptibility scales convert numbers into an assessment of a person's susceptibility as "high", "medium", or "low". Approximately 80% of the population are medium, 10% are high, and 10% are low. There is some controversy as to whether this is distributed on a "normal" bell-shaped curve or whether it is bi-modal with a small "blip" of people at the high end.[45] Hypnotizability Scores are highly stable over a person's lifetime. Research by Deirdre Barrett has found that there are two distinct types of highly susceptible subjects, which she terms fantasizers and dissociaters. Fantasizers score high on absorption scales, find it easy to block out real-world stimuli without hypnosis, spend much time daydreaming, report imaginary companions as a child, and grew up with parents who encouraged imaginary play. Dissociaters often have a history of childhood abuse or other trauma, learned to escape into numbness, and to forget unpleasant events. Their association to "daydreaming" was often going blank rather than creating vividly recalled fantasies. Both score equally high on formal scales of hypnotic susceptibility.[46][47][48]
Relaxation techniques are often integrated into other health care practices; they may be included in programs of cognitive behavioral therapy in pain clinics or occupational therapy in psychiatric units. Complementary therapists, including osteopaths and massage therapists, may include some relaxation techniques in their work. Some nurses use relaxation techniques in the acute care setting, such as to prepare patients for surgery, and in a few general practices, classes in relaxation, yoga, or tai chi are regularly available.
Since hypnotherapy is an adjunct form of therapy, used along with other forms of psychological or medical treatment, there are many applications. Hypnotherapy can be used to treat anxiety, phobias, substance abuse including tobacco, sexual dysfunction, undesirable spontaneous behaviors, and bad habits. It can be used to help improve sleep, learning disorders, communication, and relationship issues. Hypnotherapy can aid in pain management and help resolve medical conditions such as digestive disorders, skin issues, and gastrointestinal side effects of pregnancy and chemotherapy. It can also be used by dentists to help patients control their fears or to treat teeth grinding and other oral conditions.